Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

JASIN Radiosonde Data

Radiosondes were released from the ships MV Gardline Endurer, HMS Helca, RV Meteor and RRS John Murray. The ships were stationed at the northwest, northeast and south corners of a triangle of sides approximately 200km. During Phase 2 (20 August to 5 September) of the measurement programme a fourth ship was located at the centre of the triangle. The approximate positions were:

Ship

Position

MV Gardline Endurer

60° 15' N 14° 30' W

HMS Hecla

60° 15' N 10° 30' W (not between 29 July and 9 August)

RRS John Murray

60° 15' N 10° 30' W (between 30 July and 9 August)

RV Meteor

59° 00' N 12° 30' W

RRS John Murray

59° 58' N 12° 30' W (between 20 and 30 August)

The absolute position of each radiosonde ship was known to ±1km at the beginning of each radiosonde ascent. A position fix was taken every 30 minutes during the intensive radiosonde periods.

VIZ 1223 radiosondes were used, in which the rod thermistor, carbon hygristor and aneroid pressure sensor were sampled sequentially every 0.8seconds. Winds were measured by tracking the balloon with the use of LORAN-C signals retransmitted by the radiosonde. Balloons were filled with helium so as to give a rate of ascent of 5 to 6 m/s. Four radiosonde flight rigs were used:

B single balloon tracked until burst

T single balloon tracked until tropopause

TC as T, but cut down at 200mbar

P single balloon with 500mbar release and parachute, tracked during ascent and descent

Great care was taken to minimise systematic differences between ships. All radiosondes used were obtained from a single batch and the factory calibrations were used to avoid any systematic biases in the shipboard calibrations performed before launch.

Accuracy of Radiosonde Sensors

Variable

Sensor

Factory Specified Accuracy

Temperature

VIZ 1366-211

±0.1K (rms)

Relative Humidity

VIZ 1386-060

±2% (rms)

Pressure

VIZ 1292-213

within 1mbar

All data were recorded onto magnetic tape, with similar Beukers W-3 system LO-CATE ground equipment on each ship and post-experiment processing was performed at a single site.

Intercomparisons were carried out on 22 July, 23 July, 28 July, 9 August, 20 August and 5 September. Where possible each intercomparison flight was tracked by each of the ships. Unfortunately equipment failures and tracking problems resulted in the loss of much intercomparision data during Phase 1 (22 July to 9 August), particularly in the first inter- comparison period. The flight data were processed using the standard JASIN radiosonde processing system and comparisions limited to cases of ships tracking the same radiosonde.

Temperature and humidity data were corrupted by signal breakup at low transmitted modulation frequencies from the radiosonde. This corresponds to humidities above about 80 per cent and temperatures of below -40 °C. This was caused by an unexpected change in the design of the radiosondes by VIZ which resulted in different signal characteristics from those of the sample sondes tested prior to the experiment. This prevented some radiosonde tracking and all of the sets had to be retuned. Those on Hecla and Gardline Endurer were retuned at the start of Phase 1 and all sets were retuned in Glasgow between Phases 1 and 2. No corrections have been made for the temperatures. A correction procedure was developed for the Phase 2 humidities based on the fact that signal breakup was negligible for Hecla for Phase 2. Thus Hecla data have been used as a standard to which the other data have been corrected. Application of these corrections to Phase 1 data shows that further correction is needed. Corrections for Hecla are difficult to evaluate since for most of the flights a parallel resistance was incorporated into the hygristor circuit to prevent signal breakup, however this was not done at the intercomparisons.

The main conclusions of the intercomparison exercise are summarised below:

Errors due to the reception, recording and processing of the radiosonde data are 0.05 ±0.04m/s for each wind component, less than 0.05K for temperature and less than 1 per cent for humidity after corrections applied.

The standard deviation of the differences between individual 5mb values was about 0.5m/s for winds, less than 0.1K for temperature and 5 per cent for relative humidity after correction.

The true accuracy of all variables will be affected by errors not included in these figures. Only Phase 2 humidity values have been corrected.

The launch number for each ship is of the form j78snnn, where s is a ship code as follows:

Joint Air Sea Interaction Experiment (JASIN)

The JASIN Project was designed to study the interaction of the atmospheric and oceanic boundary layers with the larger scale motions of the sea and the air.

The primary aims may be summarized as follows:

To observe and distinguish between the physical processes causing mixing in the atmospheric and oceanic boundary layers and relate them to the mean properties of the layers.

To examine and quantify aspects of the momentum and heat budgets in the atmospheric and oceanic boundary layers and fluxes across and between them.

The multiplicity of processes to be sampled necessitated a large experiment and JASIN involved 14 ships and 3 aircraft with more than 50 teams of investigators from 9 countries. Altogether 35 mooring systems were deployed.

The experiment lasted for 2 months from mid-July to mid-September 1978 and comprised 2 intensive measuring periods preceded by a preparatory test period. The project took place in the north Rockall Trough, an area of deep water (1000m - 2000m) several hundred kilometres off the west coast of Scotland.